Stimulation of mitosis in thymocytes by concanavalin-A is accompanied by enhanced glucose transport. Inhibition of growth in thymocytes by glucocorticoids is accompanied by reduced glucose transport. Goals of this project are (a) to determine the significance of these glucose-transport modulations with respect to the anabolic responses and (b) to determine what we can of the mechanisms by which concanavalin-A and glucocorticoids alter transport activity. To determine the significance of glucose transport modulations, we will examine the functional relationships among external glucose, glycolytic rate, glycolytic intermediates, indices of energy status, and macromolecular synthesis in the absence and presence of concanavalin-A and glucocorticoids. To determine the sequence of events leading to transport modulations, we will test for interference by drugs with reasonably defined target systems and by hormones. Cyclic nucleotides, Ca ions fluxes and other possible mediators of transport regulation will be measured under these conditions to identify those which correlate well with transport activity. Transport kinetic studies will be carried out in hopes of disclosing the kind of interaction between final regulator and the glucose carrier. Compartmental analysis of methylglucose equilibration in conjunction with autoradiography has revealed two very different cell types in thymocyte populations. Several of the studies described above must await isolation of the sub-population which is inherently quiescent but subject to stimulation.